Silencers for jet engines



Aug. 2, 1966 J. BARTEK ETAL SILENCERS FOR JET ENGINES Filed July 30,1964 4 Sheets-Sheet 1 Fig; 1a

Aug. 2, 1966 J. BARTEK ETAL SILENCERS FOR JET ENGINES 4 Sheets-Sheet 2Filed July 30, 1964 6 VHL vHIL.

2, 1966 J. BARTEK ETAL 3,263,931

SILENCERS FOR JET ENGINES Filed July 30, 1964 4 Sheets-Sheet 3 Fig,10

Aug. 2, 1966 J. BARTEK ETAL SILENGERS FOR JET ENGINES Filed July 30. 1964 4 Sheets-Sheet 4 United States Patent 3,6 9 Claims. (Cl. 239-26511)The invention relates to the devices known as silencers which enablesthe noise of aircraft jet engines, and more particularly that ofsupersonic jet aircraft, to be reduced.

The operation of heavy civil aircraft equipped with jet engines having apowerful thrust is accompanied by considerable noise, due to thedissipation of a great part of the energy of the ejection jet in theair.

This drawback is all the more serious as the engines must operate atfull speed at the moment of take-off, that is to say, at low altitude.The maximum noise is therefore produced close to the inhabitated areasbordering airports, which thus suffer the disastrous physiologicaleffects thereof.

It has already been proposed to introduce into a jet, at the rear of thenozzle, a fluid which serves to reduce the noise.

To this end it is known to locate in the nozzle an inlet conduit forambient air which is picked up externally, this conduit opening into thejet at the rear of the nozzle. In known devices the air inlet conduit isfixed in the nozzle, so that it creates permanent obstructions in thejet, both inside the nozzle and outside it. The presence of theseobstructions, although acceptable on take-off for reducing the noise, isundesirable in cruising flight, where efficiency is of prime importance.

According to the present invention, the silencer effect is obtained, atleast on take-off, by means of tubes of circular or profiledcross-section, the upstream end of each of which is subjected to theambient pressure at the external periphery of the nozzle, or in thevicinity of this periphery,

and the downstream end of each of which opens into the jet outside thenozzle, means being provided for retracting the said tubes at will inorder to reduce or clear the space occupied by them in the nozzle and/orin the jet.

Research aimed at better operation of aircraft of the above-mentionedkind has resulted in them being provided with a nozzle of variablecross-section on which the mounting of this device is possible by reasonof its advantageous design. The downstream ends of the tubes thereforeopen into the jet, at least in the closed position of the nozzle, thatis to say in that condition of the latter which offers the minimumoutlet orifice, and control of the spreading of the tubes can becombined with control of the opening of the nozzle.

In one form of embodiment, the silencer device is fast with the nozzleand preferably with the movable elements which adjust its outletcross-section. This device, and in particularthe operation thereof, mayalso be independent of the outlet cross-section of the nozzle.

The description which follows with reference to the accompanyingdrawings, which is given by way of nonlimitative example only, willenable the various features of the invention and the manner of carryingthem into effect to be clearly understood, any arrangement appearingboth from the text and from the drawings falling within the scope of thepresent invention.

FIGURES 1 and 2 show a first embodiment of the invention in longitudinalsection through the nozzle, the respective figures showing two differentarrangements of the nozzle;

FIGURES 3 and 4 are end views in the direction of the arrows F and F inFIGURES 1 and 2 respectively;

FIGURES 1a and 3a are half views, corresponding to the views of FIGURES1 and 3, respectively, but showing a modified form of the firstembodiment employing tubes of non-circular cross-section;

FIGURES 5 and 6 are views corresponding to FIG- URES 1 and 2 showing asecond embodiment;

FIGURES 7 and 8 are transverse sectional views on the lines VIIVII andVIIIVIII, respectively, of FIG- URE 5;

FIGURES 9 and 10 are views corresponding to FIG- URES 5 and 6 butshowing a modified form of the second embodiment;

FIGURES 11 and 12 are sectional views on the lines XIXI and XII-XII,respectively, of FIGURE 9;

FIGURES 13 and 14 are views corresponding to FIG- URES 5 and 6 showinganother modification;

FIGURES 15, 16 and 17 are sectional views on the lines XV-XV, XVIXVI andXVII-XVII, respectively, of FIGURE 13.

Referring to the drawings, FIGURES 1 to 4 show a device of simpleconstruction in which the tubes are fixed to the adjustable nozzle of anaircraft.

The nozzle comprises in known manner a duct 1 to which there arearticulated outlet flaps 2 producing an outlet orifice 2a of variablecross-section. In FIGURE 1, the nozzle is open and emits a jet of largediameter; this arrangement is employed at the cruising speed of theaircraft. In FIGURE 2, the nozzle has been closed by pivoting of theflaps 2 and the cross-section of the orifice 2a determined by the latterhas thus been reduced so that the jet emitted j, is restricted, thisarrangement being employed at take-off.

The silencer arrangement comprises a plurality of elbowed tubes 3distributed regularly over the cross-section of the nozzle. To this end,certain of the flaps 2 have apertures 3a formed in them in which theelbowed tubes 3 are welded. The latter arc open upstream at 3b, at theouter periphery of the nozzle, and their downstream ends 3c open intothe jet j to the rear of the outlet orifice 2a in a zone where the jetis sufficiently expanded for the static pressure to be little differentfrom the ambient pressure. Air is drawn in by induction at the upstreamend of the tubes and is discharged at 30 into the jet.

Under the conditions of operation which prevail at take-off (FIGURE 2),the tubes 3 penetrate deeply into the jet and the air discharged at 30in the vicinity of the central zone of the jet reduces the kineticenergy thereof sufiiciently to decrease its sound energy veryconsiderably. When the nozzle fiaps 2 are operated in order to change tocruising speed conditions (FIGURE 1), the flaps carry the tubes 3 withthem and the latter move away from, or spread open radially relativelyto, the axis X-X 0f the nozzle, thus reducing the bulk of the materialobstruction which they form in the nozzle and in the jet. In thearrangement of FIGURE 1, the tubes still open into the jet at 36,although they are arranged less deeply therein, and they still produce asilencer effect, but the loss of thrust due to the presence of the tubes3 is substantially lower with the nozzle open (as in FIGURES 1 and 3)than with the nozzle closed (as in FIGURES 2 and 4).

FIGURES 1a and 3a illustrate the application of the device, theprinciple of which has just been described, to the ejection nozzle of acivil aircraft. In this application, the tubes 3 are suitably profiledso as to reduce the obstruction in the nozzle and in the jet. Twelvetubes 3 are provided which are spaced angularly from one another at 30intervals FIGURE 3a). The outlet flaps, which are articulated to theduct 1 of the nozzle in known manner at 1a, comprise twelve flaps 2bhaving aperatures 3a Patented August 2, 1966 in which the tubes 3 arewelded, as has been stated above, and twelve flaps 20 which areconnected in known manner to the flaps 2b so as to overlap them and forma deformable surface with them, the flaps 20 causing the flaps 2b topivot above their respective articulations.

To control the pivoting of the flaps 20, a ring 4 is provided slidingaxially around the duct 1 of the nozzle and connected to these flaps 20by connecting rods 6a. The sliding of the ring 4 is controlled by jacksdistributed at regular intervals around the duct 1, the rods 6 of whichjacks are articulated to the said ring 4. By actuating the jacks 5opening or closing of the nozzle is produced. The jacks drive the ring 4in translation and the latter causes pivoting of the flaps by means ofthe connecting rods 6a, the flaps 20 carrying with them the flaps 2b towhich the tubes 3 are fixed. In FIGURES 1a and 3a the nozzle closedposition of the tubes 3 is shown by dash lines.

The inlet 3b of each tube 3 is provided with vanes forming a grille 3dwhich guides the flow of incident air as it enters the tube 3 in thedirection of the arrows f.

In the embodiment shown in FIGURES 5 to 8, the tubes are movable withrespect to the adjustable nozzle. They are located outside the nozzleand, when they are placed in the positions in which they perform theirsilencing function, their downstream ends penetrate into a zone of thepropulsive jet where the pressure is not substantially higher than theatmospheric pressure.

As in the preceding figures, the duct 1 supports the movable flaps 2 ofthe adjustable nozzle, but the shifting of these flaps is independent ofthat of the silencer tubes.

The ring 4 surrounding the duct 1 can be driven in axial translation bymeans of the jacks 5, the rods 6 of which are connected to lugs 7 weldedto the ring 4. The tubes 3 are provided at the front with studs 9 bymeans of which they are articulated in yokes 8 Welded to the ring 4. Thetubes 3 are also provided with studs 10 which slide in inclined slots 11constituting slideways, which are formed in yokes 12 welded to theduct 1. The tubes 3 are open at their upstream ends at 311 and, as willbe seen in the drawing, the Open ends thereof are located in thevicinity of the external periphery of the duct 1 of the nozzle. They arebent inwardly in such manner that the open downstream end of each tubepenetrates into the interior of the jet 1' or 1' downstream of theoutlet orifice 2a of the nozzle, when the ring 4 and the tubes 3 whosedisplacement it controls are in the extreme rearward position shown inFIGURE 5.

To retract the silencer, the jacks 5 are actuated so that they bring thering 4 back towards the front, the ring carrying the tubes 3 with it, sothat they pivot at 9 in the yokes 8 while the studs 10 slide in theslideways 11, the latter being suitably inclined so that the tubes 3pivot outwardly as they slide towards the front, in such manner that thedownstream end 3c of each tube is brought into a position outside thejet (FIGURE 6).

This form of silencer device can operate both with the nozzle closed andwith the nozzle open, that is to say both on take-off and in cruisingflight, and it has the advantage that in the retracted position there isno loss of thrust of the jet engine, the tubes being outside the jet.

It will be observed that the tubes are completely outside the nozzle andthat, consequently, even in the operative position (FIGURE 5), they donot alter the profile of the nozzle.

The arrangement shown in FIGURES 9 to 12 enables the amplitude ofpivoting of the tubes 3 to be increased owing to the provision of asupplementary slideway. In this arrangement likewise, the duct 1supports the movable flaps 2 of the adjustable nozzle and theiroperation is independent of that of the silencer.

As in the case of the construction shown in FIGURES 5 to 8, the ring 4moves axially under the action of the jacks 5, the rods of which areconnected to the lugs 7 fixed to the ring 4, and the tubes 3 arearticulated in the yokes 8 of the ring 4 by means of the studs 9. InFIG- URES 9 to 12, however, the yokes 12 on the nozzle duct 1 also haveslots 13 forming slideways parallel to the axis X-X', which serve toguide the ring 4 during its translational movement. To this end, thesides 8a and 8b of the yokes 8 of the ring have holes through which thestuds 9 of the tubes extend and these studs enter the slots 13, thestuds being slidable in the slots 13 while being free to pivot in thesaid holes.

The movement of introducing the tubes into the jet is obtained bysliding the studs 10 of the tubes in the slideways 11a of the yokes 12,which slideways are similar to the slideways 11 of FIGURES 5 to 8 butare arched and more inclined with respect to the axis X--X.

To operate the silencer, the ring 4 is made to slide towards the rear tointroduce the tubes into the jet (as in FIGURE 10) or towards the frontto withdraw them therefrom (as in FIGURE 9). During this movement, thestuds 10 slide in the slideways 11a, while the studs 9 pivot in theyokes 8 and slide in the slideways 13.

As will be seen from the drawings, this form of construction isparticularly advantageous in cases in which, from the point of view ofinstallation, the space occupied downstream to the outlet plane of thenozzle must be small.

FIGURES 13 to 17 show a modified form of the arrangement shown inFIGURES 10 to 12, in which one and the same group of jacks controls boththe tubes of the silencer and the flaps of the nozzle. In thearrangement of FIGURES 13 to 17, a third series of slideways 14 carriedby lugs 15 fixed to the outside of the flaps 2 permits the latter to becontrolled by means of the tubes 3 which are themselves controlled bythe jacks 5, the control of the flaps 2 being effected by pins 16 whichare carried by the tubes 3 and slide in the said slideways 14.

It will be understood that during the movement of translation androtation of the tubes 3, which has been described hereinbefore withreference to FIGURES 10 to 12, the pins 16 carried by the tubes, whilesliding in the slideways 14, carry the latter with them, and with themalso the flaps 2 to which the slideways 14 are fixed, the flaps pivotingabout the pivots 2b of the flaps, either towards the inside when thetubes 3 are advanced into the jet (as in FIGURE 14), or towards theoutside when the tubes are withdrawn from the jet (as in FIGURE 13).

We claim:

1. A device for reducing noise arising from a supersonic jet emitted bya nozzle, comprising a plurality of tubes the each having an inlet endwhich is subjected to the ambient pressure adjacent to the externalperiphery of the nozzle, and an outlet end which opens into the jet at apoint substantially spaced downstream of the nozzle, and retractingmeans for moving said tubes away from the axis of the jet at will, atleast at their outlet end portions.

2. A device according to claim 1, for reducing noises arising from asupersonic jet emitted by a nozzle having an outlet orifice adjustablebetween an open position and a closed position, wherein the outlet endsof the tubes open into the jet, at least in said closed position of thenozzle, and means are provided for simultaneously effecting the openingof the nozzle and the moving apart of the tubes.

3. A device according to claim 2, wherein flaps are provided foradjusting the outlet orifice of the nozzle and the tubes are fast withsaid flaps.

4. A device according to claim 3, wherein the tubes are fixed to theflaps in the vicinity of the inlet ends of the respective tubes, each ofwhich opens outside the flaps.

5. A device according to claim 1, wherein the tubes are arranged aroundthe nozzle outside the latter and the retracting means are provided forshifting the tubes between a position in which their outlet endspenetrate into the jet and a position in which said outlet ends areretracted beyond the jet.

6. A device according to claim 5, wherein the tubes are mounted in suchmanner as to be able to slide axially with respect to the nozzle whilepivoting, so that during pivoting their outlet ends move nearer to oraway from the axis of the nozzle.

7. A device according to claim 6, wherein the tubes are pivotallymounted on pivoting supports which slide axially along the nozzle,elements being provided on the tubes to co-operate with elements mountedon the nozzle in such manner as to cause the tubes to pivot when saidpivoting supports are displaced in translation and means being providedfor simultaneously controlling the sliding of all the pivoting supportsalong the nozzle.

8. A device according to claim 6 for reducing noise arising from asupersonic jet emitted by a nozzle having an adjustable outlet orificecomprising a single control 9. A device according to claim 8, whereinflaps are provided for adjusting the outlet orifice of the nozzle andmeans are provided for connecting the flaps to the tubes in such mannerthat the displacement of the tubes 5 controls the orientation of theflaps.

References Cited by the Examiner UNITED STATES PATENTS 1,382,690 6/1921Stokes 181-43 2,697,907 12/ 1954 Gaubatz 60-35.6 2,982,092 5/1961 Keen6035.6

MARK NEWMAN, Primary Examiner.

device for simultaneously effecting the shifting of the tubes 15 RALPHD. BLAKESLEE, Assistant Examiner.

and adjusting of said outlet orifice.

1. A DEVICE FOR REDUCING NOISE ARISING FROM A SUPERSONIC JET EMITTED BYA NOZZLE, COMPRISING A PLURALITY OF TUBES THE EACH HAVING AN INLET ENDWHICH IS SUBJECTED TO THE AMBIENT PRESSURE ADJACENT TO THE EXTERNALPERIPHERY OF THE NOZZLE, AND AN OUTLET END WHICH OPENS INTO THE JET AT APOINT SUBSTANTIALLY SPACED DOWNWSTREAM OF THE NOZZLE, AND RETRACTINGMEANS FOR MOVING SAID TUBES AWAY FROM THE AXIS OF THE JET AT WILL, ATLEAST AT THEIR OUTLET END PORTIONS.